1. Field of the Invention
The present invention relates to a caulking gun, and more particularly to an electrical caulking gun having high operation efficiency.
2. Description of Related Art
A conventional electrical caulking gun uses electrical power and a transmission device to drive a pushing rod into a tube to release silicone out from the tube to adhere the silicone onto an object for filling in or repairing. The conventional electrical caulking gun has a speed changing device to changing the moving speed of the pushing rod so as to release the silicone at different speeds.
In addition, after the silicone has been used up, the pushing rod has to be pull backward to the original position for replacing the used tube with a new one. For easily pulling the pushing rod to move backward, a clutching device is mounted on the conventional caulking gun to clutch the transmission device.
The clutching device of the conventional caulking gun is connected to the trigger of the conventional caulking gun. Before the trigger is pulled, the clutching device is disengaged from the transmission device and the transmission device is at a neutral gear stage. Therefore, the pushing rod can be moved backward easily. When the trigger is pulled, the clutching device is engaged with the transmission device to make the transmission device at the driving stage, such that the electrical power can be transmitted to the pushing rod via a motor and the transmission device to release the silicone. At this time, the pushing rod cannot be pulled backward manually due to the engagement between and the limitation provided by the transmission device and the motor.
However, the conventional clutching device connected to the trigger has to reengage the transmission device each time of the trigger being pulled, so the operation of the caulking gun may be delayed due to the reengaging time between the clutching device and the transmission device. Thus, the operation efficiency of the caulking gun is badly influenced and reduced.
In addition, the speed changing device of the conventional caulking gun can change the moving speed of the pushing rod to release the silicone at different desired speeds for different work needs. At the end or corner of the releasing travel of the silicone, the releasing speed of the silicone has to be slowed down to make the silicone to be adhered onto the end or corner evenly. However, the speed of the pushing rod cannot be changed during the movement of the pushing rod and only can be changed after the conventional caulking gun being stopped and then adjusted by the speed changing device. Accordingly, the release of the silicone is broken off and is not smooth, and the silicone cannot be adhered on the object evenly.
To overcome the shortcomings, the present invention tends to provide a caulking gun to mitigate or obviate the aforementioned problems.